1. Field of the Invention
The present invention relates to a recording liquid suitable for use in the ink jet recording process in which droplets of recording liquid called an ink are flown from a recording head through its orifices to perform recording, or for other recording by means of a writing tool, and more particularly to a recording liquid giving an ideal black or blue black color.
2. Description of the Prior Art
Ink-jet recording generates less noise and permits a high speed recording on plain paper without the necessity for any special fixing treatment, so that various types of ink-jet recording systems are being investigated energetically.
The recording liquid used for these ink jet recording systems needs to fulfill the following requirements such that its physical properties such as viscosity, surface tension, etc. should be each within a proper range, it should not clog a fine spout (orifice), it should form images of bright color tone and of sufficiently high optical density, and it should not undergo a change in physical properties or deposit solid matter, during storage.
In addition, the recording liquid is desired to meet the following requirements as recording therewith should be accomplished without particular restriction of the kind of recording medium, including paper, which is the most typical recording medium, it should exhibit a high rate of fixing on recording media, it should give images excellent in resistances to water, solvent (particularly alcohol), light, and attrition, and it should form images with a high degree of resolution.
Since the recording liquid used for ink-jet recording is composed basically of a cloloring component dye and its solvent, the above performance characteristics required are much affected by inherent properties of the dye. Accordingly, it is very important in the art to select a dye so as to provide the recording liquid with the above performance characteristics.
The solubility of the dye in the liquid medium is particularly important; it is essential for maintaining a good anti-clogging property and solution stability of the recording liquid that the dye be sufficiently soluble in water as well as in the wetting agent used, which is generally composed of an organic solvent.
On the other hand, for performing black color printing, a recording liquid giving a primary black color or a primary blue black color is used. Furthermore, for reproduce full-color recorded images, recording liquids of four primary colors including three primary colors (magenta, yellow and cyan) and a black primary color are used, wherein the color tone of a recorded image is governed by subtractive mixing of these recording liquids. In order to form images of desired color tone, it is required that these recording liquids of three primary colors have ideal hues of primary colors, as magenta, yellow and cyan without a tinge of any other color, and also that the black recording liquid has pure black color tone without a tinge of any other color. Therefore, it is also very important in the art to select properly dyes as coloring component taking the color tone given by a black or blue black recording liquid into consideration.
However, almost none of the known recording liquids in black color or blue black color, satisfy the above noted requirements, particularly with respect to solubility, color tone and light resistance. Thus, a black or blue black recording liquid meeting the above requirements has been strongly desired.